Do what you want, but you loose a large percentage of light when you
hang it over a tank....more than what you really t hink yu do. I
played around with a PAR and a LUX meter, and its unreal how much
light you loose. Its also unreal how much light you loose when it is
placed above a piece of glass as well.....Lots of folks use what is
called egg crate (a white or black plastic grill used in suspended
ceilings to create a diffuser for the lights, and believe it or not,
you loose 46% + of useable light just passing through this egg crate
grill and you can loose more if the grill is placed improper side
up...Its also unreal how much light is actually spilling out the sides
but it appears to look like its going down through the tank and out
the sides, when in fact it is not even entering the tank, its all
outside the tank.

There is only one way to do it an dthat is make a totally enclosed
hood. Wood is fine, and can easily be made out of 1x6. Paiant inside
white for best surface reflection (actually white is better than
mirrow is, unless you use a proper reflector, go with white paint.

You can buy a Power compact flourescent electronic ballast on line
(about $20) complete with socket that wil fire a 24 to 65 watt PC
bulb which is available in all kinds of color (kelvin temps) which is
more suitable and better than the typical tube type flourescent
lights, unless your going with T5 type.....which would be way overkill
for FW setups anyhow.......You can also buy a decent ballast at Home
Depot complete with wiring diagram for under $5 that will power up a
65 watt PC bulb. Around here we can get 34-65 watt PC bulbs of varous
kelvin for 10 to 16 bucks.......much better than any shop light or so
called plant growing bulbs .......I use 6700 to 7200 and on occassion
10K PC lights and all my plants do great.......I do not have any
lights over glass, or egg crate. I use home brew hoods I make out of
acrylic plastic, but like I said, wood is fine if its sealed....and
painted white inside for reflection unless a proper reflector is
used......




On Tue, 13 Mar 2007 10:40:40 -0500, cailinsdad
wrote:

On Tue, 13 Mar 2007 10:25:27 -0500, "Reel McKoi"
wrote:

My question, is it reasonable to hang the light a few inches above a
glass top or is it necessary for the light to rest right on the glass?

Mine rest right on the tank rim but would be better a few inches off the
top. I lost the spacers I had that held them above the rim by 2".

Cool. I was planning to hang the light about 2-3 inches from the
glass.




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I forgot more about ponds and koi than I'll ever know!